From North Carolina northward to Maryland, Brood II
cicadas are now up in the treetops chorusing to win the affections of their
mates. In previous episodes we
learned about the cicada’s dismal seventeen year internment as nymphs
underground sucking on the xylem fluid of plants. During the past several weeks,
millions of nymphs vacated the earth through their exit tunnels and dashed to
vertical structures to shed their nymphal
exoskeletons and emerge as adults. Within hours of this remarkable
transformation, the adult’s appearance transforms from pale white to jet black
as its exoskeleton hardens. Males and females quickly climb to the treetop to
begin their courtship ritual. Male cicadas require from five to eighteen days
before they begin calling and enter the mating game. To make the sounds necessary to woo his mate,
male cicadas evolved unique structures called tymbals. These paired organs are
located on the sides of their bodies just beneath the wings. Muscular
contractions vibrate the membranous tymbals much like a drumhead to produce
sound - and the sound they produce can be prodigious! Recorded at 90 decibels
or more, cicada singing is as loud as a lawn mower engine or jet aircraft.

By vibrating the tymbal, the male cicada produces squawk and courtship calls.

Chorusing of thousands of cicadas in the treetops produces other-worldly sounds.

Males produce a variety of
calls for different purposes. If threatened by a predator such as a bird or a
squirrel, a loud squawking noise is made in an attempt to startle the predator
and make an escape. However, the principal function of the tymbal is to produce
calls that assist in attracting a mate and winning her affection. Since some emergences
of periodical cicadas can include as many as four different species, one type
of call attracts both males and females of the same species to a common
assembly place such as a large tree. When the guys and gals get eye to eye, the
male will use three distinct and different courtship songs to try and convince
the gal that she should be the mother of his nymphs. If the lady likes his
advances, she will signal her approval by flicking her wings, often with an
audible click. After coupling for an hour or more, the male cicada inserts a
copulatory plug into his mate, thereby curtailing further inseminations by
other suitors. In a deal that seems patently unfair, it is believed that the
male cicada then moves on and mates with other females. In the next episode of Bug
of the Week, we will explore another chapter in the life of what may be the
most fascinating member of the insect world, the periodical cicada.

References

This week’s episode was inspired by the crew of “Cicadas and
Invaders,” a special production of Discovery Science. The wonderful article by K. S. Williams and
C. Simon “The ecology, behavior, and evolution of periodical cicadas” was used
as a resource for this episode.

To view
other recent episodes of Bug of the Week that explore Brood II, and other
excellent websites dedicated to cicadas, please click on the following links: